package com.exam.system.token;

import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @ClassName JWTFilter
 * @Description 继承官方的BasicHttpAuthenticationFilter，并且重写鉴权的方法
 * 代码的执行流程preHandle->isAccessAllowed->isLoginAttempt->executeLogin
 * @Author ckl
 * @DATE 2021/5/24 13:06
 * @versions 1.0
 */
@Component
public class JWTFilter extends BasicHttpAuthenticationFilter {

    /**
     * 先执行的方法
     * @param request
     * @param response
     * @return
     * @throws Exception
     */
    @Override
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
        httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
        httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
        // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
        if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
            httpServletResponse.setStatus(HttpStatus.OK.value());
            return false;
        }
        return super.preHandle(request,response);
    }

    /**
     * 是否允许用户访问
     * @param request
     * @param response
     * @param mappedValue
     * @return
     */
    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        if (isLoginAttempt(request, response)){
            try {
                // token存在
                return executeLogin(request, response);
            } catch (Exception e){
                // token不存在
                response401(request, response);
            }
        }
        return true;
    }

    /**
     * 判断用户是否已经登入
     * @param request
     * @param response
     * @return
     */
    @Override
    protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        String authorization = httpServletRequest.getHeader("Authorization");
        return authorization != null;
    }

    /**
     * 验证登录是否成功
     * @param request
     * @param response
     * @return
     * @throws Exception
     */
    @Override
    protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        //从请求头中获取token
        String authorization = httpServletRequest.getHeader("Authorization");
        //放入对象中, redis或者数据库查询  等同于之前的UsernamePasswordToken
        MyJsonWebToken token = new MyJsonWebToken(authorization);
        // 提交给realm进行登入，如果错误他会抛出异常并被捕获
        System.out.println("JWTFilter.executeLogintoken交给realm判断:"+token);
        //这个等同于直接的 subject.login(token)
        getSubject(request, response).login(token);
        // 如果没有抛出异常则代表登入成功，返回true
        return true;
    }

    /**
     * 验证不成功
     * @param req
     * @param resp
     */
    private void response401(ServletRequest req, ServletResponse resp) {
        try {
            HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
            httpServletResponse.sendRedirect("/");
        } catch (IOException e) {
            System.err.println(e.getMessage());
        }
    }
}
